When a mass having angular momentum around a spin axis, has a torque applied to it around any axis that is not parallel to the spin axis, the mass is caused to rotate about an axis perpendicular to the axis of the applied torque and the spin axis, this motion is termed precession. Such torque-induced precession, also termed gyroscopic precession, is the cause of the wobbling of the axis of a spinning object and is commonly seen in a spinning top toy.
In a gyroscope, a spinning mass is gimbal mounted so that it may rotate about three axes. In particular, the gimbal mounting comprises an outer or primary frame that is pivotable about a first axis relative to a stationary mount. An inner or secondary frame is supported by the primary frame for rotation about a second axis inclined relative to the first axis. The spinning mass is in turn supported on the secondary frame by means of a spindle of which the axis is inclined relative to the second axis. In such a gyroscope, if a torque is applied in some way to cause the secondary frame to rotate with respect to the primary frame, then the primary frame will also experience a torque causing it to rotate.
The torque converter of the present invention is based on this same principle that if a torque from an input shaft is applied to one of the two frames of a gimbal mounted spinning mass then the other frame will experience a torque which can be applied to an output shaft to serve as output torque.
However, if the mass is spinning constantly in the same direction within the secondary frame and a torque is applied to make the secondary frame rotate always in the same direction with respect to the primary frame, then the direction of the resultant torque on the primary frame will oscillate at a frequency determined by the speed of rotation of the secondary frame within the primary frame. This is because the direction of the torque depends on the direction in which the angular momentum vector is pointing. An additional step needs therefore to be taken if one is to produce a torque converter in which the input and output shafts both rotate constantly in the same direction.
There are different approaches for achieving this objective, which are considered below. In particular, in order to maintain a constant output, a torque converter must resort to one of the following possibilities, namely:
(i) Oscillating primary frame
(ii) Oscillating secondary frame
(iii) Oscillating Masses
(iv) Variable Moment of Inertia (no examples)
Examples of the first three approaches have been proposed in the prior art and are discussed below. The fourth is mentioned here only as a theoretical possibility because it appears not to have been attempted and, indeed, is not used in the present invention.
(i) Oscillating Primary Frames
In U.S. Pat. No. 6,729,197, a continuously rotating flywheel is mounted in a sub-frame, which is itself driven continuously from an independent axle, via gearing. The main frame experiences an oscillating torque which drives an output shaft. A one-way roller clutch is used to rectify the motion of the output shaft.
In U.S. Pat. No. 4,161,889 and WO 2005/071257 are other examples of the oscillating primary frame type.
(ii) Oscillating Secondary Frames
WO 00/45068 discloses a device which consists of an inertial body mounted on a linkage, which is cyclically deflected. The reaction forces generated by the inertial body as it is being cyclically deflected are applied to a torque shaft. The motion is rectified using two one-way clutches and some gearing.
Other prior art references which rely on oscillating secondary frames include AU 2004100816, U.S. Pat. No. 4,361,055, DE OS 2,105,939, DE 2,126,292, SU 1174641, U.S. Pat. No. 3,851,545, WO 04/003405, and GB 1,421,309. As the present invention does not use an oscillating secondary frame, the latter patents are mentioned only for completeness and need not be described in detail.
(iii) Oscillating Masses
As will be described in more detail below, this is the approach adopted by the present invention and accordingly the references discussed below are believed to constitute the most pertinent prior art.
WO 93/17261 discloses one or more inertial masses or flywheels mounted in a secondary frame, which is in turn mounted in a primary frame. The reference assumes that when the primary and secondary frame are both rotated simultaneously, the inertial mass will experience an oscillating torque around the spin axis, that is at a maximum when the spin axis is at right angles to the primary axis. It is noted in the reference that that the assumed angular motion of the inertial masses is 90° out of phase from that required to generate continuous gyro torque between the primary and secondary frames. Each flywheel is therefore coupled to a pump which drives a hydraulic fluid through a hydraulic line that passes along the secondary frame axle, through a seal and then along the primary frame to a turbine mounted on the primary frame shaft. The hypothesis is that the pumps create a phase difference in the flywheel motion due to the damping of the hydraulic system, the energy being recycled to the device via the turbine. The reference also proposes the use of two helical springs per flywheel mounted between lugs on the flywheel and lugs on the secondary frame, to assist the vibration.
The assumption made in the patent that when the primary and secondary frames are both rotated simultaneously the inertial masses will experience an oscillating torque around their spin axis is believed not to be correct. Experimental attempts by the present inventor to cause flywheels to oscillate in this manner proved unsuccessful and this can also be shown mathematically to be an erroneous assumption.
DE 4,337,858 discloses three oscillating masses arranged at 120° angles around the secondary axis. The oscillation is driven by a reciprocating rod mounted in the primary frame shaft. The rod connects to the masses via a system of cams, gears and pin jointed rods.